1. Field of the Invention
The present invention relates to an improvement in a strobe charge apparatus which is equipped in, e.g., a camera, and comprises a flyback booster circuit.
2. Description of Related Art
Conventionally, an embodiment of Published Japanese Translation of a PCT Application No. 6-504182 discloses a booster circuit shown in FIG. 25. This prior art discloses a technique for charging in a so-called continuous mode in which the ON time of a primary-side circuit is set to be a predetermined duration, the current level of a secondary-side circuit is detected by a comparator 1002 and resistor 1003, and an operation is made based on detection of a predetermined current level.
However, in the prior art described in Published Japanese Translation of a PCT Application No. 6-504182, the comparator 1002 is required to detect the current that flows on the secondary side of a transformer 1001, as shown in FIG. 25. For this purpose, a comparator must be incorporated in a control IC, or a comparator element must be mounted. The resistor 1003 that makes current detection is connected to a node between ground (GND) and the transformer 1001, and a voltage is detected at a position V in FIG. 25. Therefore, V generated by the resistor 1003 when a secondary current flows has a negative potential with respect to GND. That is, a comparison voltage Vref of the comparator 1003 requires a negative potential, and a power supply arrangement which has a negative potential that forms Vref is required as a power supply of a camera. Hence, the circuit scale increases.
One aspect of the invention is to provide a charge apparatus which comprises a flyback booster circuit that intermittently supplies a current to a primary coil of a transformer, and supplies a charge current from a secondary coil of the transformer to a capacitor during a period in which no current flows through the primary coil, wherein the apparatus includes, as a detection circuit arrangement for detecting a current that flows through the secondary coil, a switching element which changes from a first state to a second state when the current that flows through the secondary coil becomes equal to or lower than a predetermined value, and current supply to the primary coil starts in response to switching of the switching element from the first state to the second state.
One aspect of the invention is to provide a charge apparatus, which has, as a detection circuit arrangement for detecting a current that flows through the secondary coil, a first diode, the cathode of which is connected to a terminal opposite to a terminal of the secondary coil, which is connected to a positive electrode of the capacitor, and a second diode to which the anode and cathode of the first diode are connected, and the anode of which is connected to a negative electrode of the capacitor, wherein when the detection circuit detects that the current that flows through the secondary coil becomes equal to or lower than a predetermined value, current supply to the primary coil starts.
One aspect of the invention is to provide a charge apparatus which comprises a flyback booster circuit that intermittently supplies a current to a primary coil of a transformer, and supplies a charge current from a secondary coil of the transformer to a capacitor during a period in which no current flows through the primary coil, wherein the apparatus comprises a control circuit which has a first operation mode for controlling the current supply start timing to the primary coil in accordance with a current that flows through the secondary coil, and a second operation mode for controlling the current supply timing to the primary coil independently of the current that flows through the primary coil, so as to make an appropriate charge operation.
Other objects of the present invention will become apparent from the following description of preferred embodiments taken in conjunction with the accompanying drawings.